When migrating from Lotus Domino/Notes to Microsoft Online, migration options are limited not only in product offerings but also functionality.  Coexistence is basically non-existant from the stance of a “normal” e-mail migration.  Out of the many inconveniences that this brings, one is the inability to migrate Proxy Addresses directly out of Notes accounts and in to Exchange Online mailboxes.  Microsoft requires manual entries for seconday e-mail addresses, which poses a significantly large effort for even smaller environments.  Quest and other 3rd party “Notes to BPOS” migration products are not allowed direct access to Microsoft Online AD accounts.  The only way around manual entries is to migrate the Proxy Addresses in to the on-premise Active Directory (ProxyAddresses attribute) and synchronize that information via Directory Synchronization to BPOS.  There are a few important caveats with this process:

  • A user must have never been activated in BPOS for the ProxyAddresses attribute to sync with the BPOS secondary email addresses (alias)
  • If a user is activated and assigned a license in BPOS, aliases must be manually entered
  • If a user is activated and assigned a license in BPOS and then deactivated, his aliases will not synchronize from the on-premise AD regardless of changes made to the on-premise account
  • The mail attribute is not important (can be removed) as long as the ProxyAddresses attribute is accurate
  • Use SMTP: for Primary Address and smtp: for secondary addresses in ProxyAddresses attribute
  • When a user is deleted from AD, the account gets deleted in BPOS regardless of activation status

Basically the main point is that the ProxyAddresses attribute has to be populated before the user accounts are enabled in BPOS to avoid manual entries. 

A typical mail migration from Notes requires a 3rd party product, such as Quest Notes Migrator for Exchange, to pull all the data.  Quest will provide a spreadsheet file (in .tsv format) that contains the proxy addresses for all accounts.  Using some Excel magic, one can split the single cell filled with addresses in to multiple cells, save as a .csv, and then run a script to import those addresses in to the ProxyAddress attribute.  If one can match up the samAccountName attribute to the proxy addresses, and has access to the ActiveRoles Management Shell from Quest to import data via PowerShell, the following script will do the trick (assuming proper permissions):
Connect-QADService -service ‘localhost’

$list=import-csv “c:\aliasimporttest.csv”
foreach ($name in $list)
{
$UserInfo = Get-QADUser -SamAccountName $name.samAccountName
#The following line should only be used for multivalued attributes. It reads from the existing attributes and adds additional data from the CSV file.
Get-QADUser -SamAccountName $name.samAccountName | Set-QADUser -ObjectAttributes @{proxyaddresses=@{Append=@($name.SMTP2)}}
Write-Host $UserInfo.proxyaddresses
Get-QADUser -SamAccountName $name.samAccountName | Set-QADUser -ObjectAttributes @{proxyaddresses=@{Append=@($name.SMTP3)}}
Write-Host $UserInfo.proxyaddresses
}
Disconnect-QADService

Remember that the Proxy Addresses have to have smtp: appended to them to be correctly interpreted (i.e. smtp:user@domain.com).

Once that is complete, force a DirSync, do a bulk enable of accounts and start the e-mail data migration.